Melt spinning apparatus



Nov. 6, 1962 R. F. LEES- MELT SPINNING APPARATUS Filed Nov. 23, 1960- FIG.

INVENTOR RAY E LEES United States Patent Ofifice 3,061,874 Patented Nov. 6, 1962 3,061,874 MELT SPINNING APPARATUS Ray F. Lees, Donelson, Tenn, assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Nov. 23, 1960, Ser. No. 71,194 6 Claims. (Cl. 18-8) This invention relates to novel apparatus for the production of crimped filaments of synthetic polymers. More particularly, it relates to novel apparatus for melt spinning filaments of synthetic polymers which crimp spontaneously after they have been drawn.

It has been previously recognized that crimped filaments can be prepared from certain thermoplastic polymers by extruding the molten polymers in the form of filaments, quenching the extruded filaments in an asymmetric manner so that one side of each filament is solidified before the other side, and orienting the extruded filaments. Asymmetric cooling of a filament is achieved by employing as the quenching medium a jet of air or other gas directed upon one side of the extruded filament a short distance from the spinneret rather than by cooling the filament over a considerable distance with a current of air, as in conventional melt spinning. Although the as-spun filaments are straight, they become highly crimped after they are drawn several times their spun length and the tension is released, apparently due to the stresses set up within the filaments by the asymmetric quenching step. Thermoplastic polymers which are suitable for the preparation of such quenched filaments include linear condensation polyesters such as polyethylene terephthalate and poly(p-hexahydroxylylene terephthalate), po-lyamides such as polyhexamethylene adipamide, polyolefins such as poly(vinylidene chloride) and polyethylene, and many other polymers.

In preparing a plurality of the crimped filaments, it is highly desirable that the filaments be substantially uniform, not only with respect to the degree of crimp but also with respect to dyeability and other physical properties. In the past, however, attempts to spin a large number of the filaments simultaneously have resulted in poor uniformity of the oriented, crimped yarns owing to difficulties in contacting each molten filament with quenching gas at the same velocity and temperature. The problem has been made more severe by temperature non-uniformities across the spinneret caused by the contact of the jet of quenching gas with the spinneret.

An object of the present invention is the provision of novel apparatus for spinning synthetic polymer filaments which have the property of spontaneously crimping when they are oriented. Another object is to provide apparatus from which filaments can be spun which produce a highly uniform crimped product upon drawing. Other objects will appear as the description. of the invention proceeds.

These and other objects are achieved by means of the apparatus of the present invention as set forth in the following description and claims.

Briefly described, the invention comprises a spinning apparatus provided with a spinneret containing a plurality of orifices arranged in concentric circles and means for supplying an annular jet of quenching gas, concentric with the circles of orifices and directed radially inwardly towards the outermost circle, close to the spinneret face and parallel to it. More specifically, such means may comprise an annular nozzle, concentrically surrounding the outermost circle of orifices and spaced close to the spinneret, having a vertical opening on the order of an inch in height adapted for supplying an annular jet of quenching gas parallel to the spinneret face. The circles of orifices are preferably closely spaced, with the diameter of the innermost circle being at least half of the diameter of the outermost circle. Preferably, when it is desired to employ high velocity quenching gas to achieve a high degree of spontaneous crimpability, an insulating disc is mounted against the lower face of the spinneret concentric with and having a diameter smaller than the diameter of the innermost circle of orifices.

The nature of the invention will be more readily understood by reference to the following description taken in conjunction with the accompanying drawings, in which FIGURE 1 is a sectional elevation taken through a spinneret assembly and quenching apparatus in accordance with the present invention.

FIGURE 2 is a sectional elevation of another embodiment of quenching apparatus which may be used in accordance with the present invention, together with a portion of a similar spinneret assembly, and

FIGURE 3 is a sectional elevation of still another embodiment of quenching apparatus which may be used in accordance with the present invention.

Referring now to FIGURE 1, molten polymer is introduced through inlets 1 andforced through sand pack 2, which may be built up in conventional manner from screens and various particle sizes of sand as described in US. Patent 2,266,368 to Hull et al. The polymer then flows through channels 3 in retaining member 4 and through channels 5 and annular polymer distribution space 18 in distribution member 6 to orifices 7 in spinneret plate 8. Filaments 9, which are closely spaced in a series of concentric rings owing to the dense spacing of the spinneret orifices in concentric circles, are immediately quenched by a strong flow of gas from annular nozzle 10. The gas enters the annular nozzle through conduit 11 and flows through foram-inous members 12 from vertical annular opening 19 across the filament bundle as indicated by the arrows. The spinneret is held by bolts 13 to the distribution member 6, while bolt 17 acts to hold spinneret plate 8 and the distribution member 6 to the retaining member 4 in the desired alignment. Insulation 14 is also suitably provided to minimize flow of heat from the spinneret and other members of the assembly.

FIGURE 2 shows a portion of a spinneretv assembly similar to that illustrated in FIGURE 1, together with an alternative quenching nozzle 20 which may be employed in accordance with the invention. The quenching nozzle is formed by annular member 21, which contains a hollow annular plenum chamber 22. The quenching gas enters the annular plenum chamber through conduit 23 and flows from the plenum chamber through annular diffusion chamber 24, which comprises glass beads 25 retained by screens 26. The jet of quenching, gas then passes through annular screen 27 of fine mesh and flows across the filament bundle parallel to the spinneret face, as indicated by the arrows. Annular screen 27 is suitably about 50 mesh, while retaining screens 26 may have a mesh size of 12 and the glass beads may have a diameter of about A; inch.

The quenching nozzle is adapted for downward removal from the spinneret on tracks or grooves 28 in the side of the spinning cell by means of wheels 29 mounted on the side of the annular member21, afiording ready access to the spinneret for performance of routine function's during the spinning operation. The quenching nozzle may be I held in operating position by any of various suitable locking means (not shown). A damper (not shown) may also be provided in the quenching gas supply conduit 23 for shutting off the jet of quenching gas when the quenching nozzle is lowered from the spinning position.

The same reference numerals employed in FIGURE 1 3 with respect to the spinneret assembly are employed in FIGURE 2 with respect to corresponding elements in the spinneret assembly. However, FIGURE 2 illustrates a preferred embodiment of the invention in which a circular disc 30 of reinforced insulation is provided against the spinneret face to prevent excessive cooling of the spinneret when high velocity quenching gas is used to achieve a product having a high degree of spontaneous crimp. Screw 31 threaded into the head of bolt 17 is provided to hold disc 30 against the face of the spinneret.

FIGURE 3 shows a portion of a spinneret assembly similar to that illustrated in FIGURE 2, together with another embodiment of the quenching nozzle 32 which may be employed in accordance with the invention. Reference numerals previously used in FIGURES 1 and 2 indicate corresponding elements when employed again in FIGURE 3. The quenching nozzle is formed by annular member 33, which contains lower plenum chamber 34 and upper chamber 35 separated by difl'usion chamber 24 comprising glass beads retained by screens 26. The quenching gas enters lower chamber 34 through conduit 36 and flows through diffusion chamber 24 and upper chamber 35 and thence as a jet of quenching gas through annular screen 27 of fine mesh and across the filament bundle parallel to the spinneret face. As illustrated in FIGURE 3, the spinneret assembly may be provided with band heater 37, which may be used to control the temperature of the spinneret independently of the flow of polymer, which heats the spinneret, or the quenching gas, which cools it.

In spinning and quenching with the apparatus of the invention, contact of the freshly extruded molten filaments with the jet of quenching gas provides sufliciently rapid cooling that each filament solidifies asymmetrically. By employing a radial jet of quenching gas, maximum interfilament uniformity is achieved. In accordance with the invention, the circles of orifices from which the filaments are extruded are closely spaced, with the diameter of the innermost circle being at least half of the diameter of the outermost circle. In this way, the velocity and temperature of the quenching gas contacting each filament is approximately the same, and a large central area is provided through which the quenching gas can fiow downwardly after it has contacted the filaments. Uniformity i of the spun filaments with respect to degree of crimp, dyeability, and other physical properties is greatly enhanced by the symmetrical distribution of polymer during spinning; e.g., by providing annular polymer distribution space 18 and by placing the orifices on concentric circles, as well as by radial inward movement of the quenching gas from the concentric annular nozzle.

Insulating disc 30, which has a diameter slightly less than the diameter of the innermost circle of spinneret orifices, is suitably formed of wire reinforced asbestos sheet. By employing the insulating disc, the temperature of the spinneret may be kept uniform even when the quenching gas is introduced at high velocity and the interfilament uniformity of the spun and drawn filaments is also found to be quite good. In the absence of the insulating disc, however, temperature difierentials are markedly increased, especially with high quenching gas velocity, and poor interfilament uniformity results. In the absence of the insulating disc it is frequently also difficult to maintain the temperature of the spinneret at the extrusion face above the melting point of the polymer, especially in the case of polymers melting at elevated temperatures.

The size and spacing of the annular quenching nozzle is critical. In general, the inside diameter of the annular nozzle is no more than about 4 inch greater than the diameter of the outermost circle of spinneret orifices. The nozzle opening is preferably on the order of one inch in height; i.e., within the range of about /2 inch to about 1% inches, since the air velocity required when a substantially smaller opening is used is too high, while substantially greater nozzle openings are inefiective in producing asymmetric quenching. The upper edge of the nozzle is preferably positioned within about 7 inch of the face of the spinneret.

After the filaments are spun, they may be drawn in conventional manner. For example, the filaments may be combined in the form of a tow and drawn in a hot aqueous spray. In the case of polyester yarns, a preheating bath may be used if desired as disclosed by Paulsen in his United States Patent 2,918,346, filed August 7, 1956. The filaments may also be drawn in the form of yarn bundles on conventional apparatus such as the hot pin apparatus disclosed by Kinney in his United States Patent 2,874,410. The resulting drawn filaments are characterized by a marked three-dimensional crimp and are highly useful in the production of woven and knitted staple fabrics having a desirable bulky hand and as stuifing materials for pillows and other stuifed articles.

In an actual experiment employing the apparatus of FIGURE 1, with the addition of a band heater and insulating disc as shown in FIGURE 3, a spinneret is provided having a plate containing 900 round orifices, each 0.007 inch in diameter, arranged on 6 concentric circles whose radii differ by 0.052 inch each, the smallest circle having a radius of 1.437 inches. The orifices are located at the intersections of radii of the spinneret spaced at angular intervals of 112 with the concentric circles, alternate intersections being skipped to provide a staggered pattern of orifices having center-to-center spacings on the circles varying from about 0.060 inch in the inner circle to about 0.071 inch in the outer circle. An annular quenching nozzle 4% inches in inside diameter and having an opening 0.5 inch high spaced inch below the spinneret face by a-ring of aluminum foil and heavy asbestos cloth is employed. An insulating disc 2%. inches in diameter and having a thickness of inch is mounted against the lower face of the spinneret. Polyethylene terephthalate flake having a relative viscosity of 20.6 is melted and the melt (maintained at a temperature of about 290 C.) is extruded through the spinneret. The polymer throughput is 51.4 lbs/hr. and quenching air atroom temperature is supplied at the rate of 163.5 cu. ft./ lb. of polymer. Auxiliary heat issupplied to the spinneret by an electric band heater around the circumference of the spinneret. The filaments are wound up at 400 y.p.m. A large number of the filaments are combined to form a tow, passed through an aqueous bath containing a textile finish agent, drawn 3.9x in a C. aqueous spray containing a textile finish agent, and piddled into an open container. Upon release of the tension of drawing, it is observed that the filaments exhibit a high level of threedimensional crimp. The filaments are then cut to 2.2- inch lengths and'relaxed for 15 minutes in a hot air oven maintained at 140 C. The resulting fibers are found to have a crimp level of 8.0 crimps per inch, a denier per filament of 4.2, a tenacity of 2.2 grams per denier, a break elongation of 43%, a tensile strength of 28.7 kg./mm., and a tensile recovery from 3% extension of 91%. The crimp index, a measure of the extent of crimp of a fiber or bundle of fibers, is 51%. In this measurement, the required data are obtained by measuring the length of the fibers hanging under an added load of 0.1 g.p.d. for a period of 2 seconds (length A), under which condition they are held straight, and measuring the length of the same fibers hanging under no added weight after they have relaxed for 15 seconds from the first extension (length B). The crimped tow from which the staple fibers are derived may be used in place of the fibers. The crimp index is calculated in accordance with the formula Crimp Index= A 5 may be employed with various spinneret assemblies, including any of the embodiments illustrated in FIGURES 1, 2, and 3. Many additional embodiments of the invention will be apparent to those skilled in the art, and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. A spinning apparatus adapted to spin molten synthetic polymer comprising a spinneret having a plate containing a plurality of spinning orifices arranged in circular form without orifices near the center of the plate, means for supplying a molten synthetic polymer to the spinneret, means for supplying an annular jet A2 to 1 /2" in height of quenching gas concentric with and within about A" from the outer circle of the spinning orifices for directing the gas radially inwardly uniformly around and Within about 71 of the spinneret orifices and parallel to the outer face of the spinneret plate.

2. The apparatus of claim 1 in which the spinneret orifices are arranged in a plurality of concentric circles, the innermost having a diameter at least half the diameter of the outermost circle.

3. The apparatus of claim 1 in which the outer face of the spinneret plate within the innermost concentric circle of orifices is provided with an insulating disc.

4. The apparatus of claim 1 in which the quenching gas is supplied -by an annular nozzle provided with screens.

5. The apparatus of claim 4 in which the annular nozzle is provided with a plurality of screens and the area between the screens contains glass beads.

6. The apparatus of claim 1 in which the body of the spinneret is supplied with an annular band heater and an outer layer of insulation.

References Cited in the file of this patent UNITED STATES PATENTS 2,252,684 Babcock Aug. 19, 1941 2,252,689 Bradshaw Aug. 19, 1941 2,834,046 Hesselink May 13, 1958 2,947,029 Bakker Aug. 2, 1960 FOREIGN PATENTS 796,376 Great Britain June 11, 1958 

1. A SPINNING APPARATUS ADAPTED TO SPIN MOLTEN SYNTHETIC POLYMER COMPRISING A SPINNERET HAVING A PLATE CONTAINING A PLURALITY OF SPINNING ORIFICES ARRANGE IN CIRCULAR FORM WITHOUT ORIFICES NEAR THE CENTER OF THE PLATE, MEANS FOR SUPPLYING A MOLTEN SYNTHETIC POLYMER TO THE SPINNERET, MEANS FOR SUPPLYING AN ANNULAR JET 1/2 TO 11/2" IN HEIGHT OF QUENCHING GAS CONCENTRIC WITH AND WITHIN ABOUT 3/4" FROM THE OUTER CIRCLE OF THE SPINNING ORIFICES FOR DIRECTING THE GAS RADIALLY INWERDLY UNIFORMLY AROUND AND WITHIN ABOUT 3/10" OF THE SPINNERET ORIFICES AND PARALLEL TO THE OUTER FACE OF THE SPINNERET PLATE. 